The present invention relates to an EGR (Exhaust Gas Recirculation) valve device which comprises, for example, a recycling system for exhaust gases.
Description of Related Art
Conventional examples of this type of EGR valve have been used with a stepping motor to open and close valves. However use of a DC motor instead of a stepping motor has developed in order to increase output, improve response characteristics and improve limits in the resolution of valve aperture regulation.
FIG. 1 is a longitudinal cross section of an EGR valve device as disclosed in Published Unexamined Japanese Patent Application H10-220620 (1998) for example. In FIG. 1, reference numeral 1 denotes a valve body, 2 denotes a motor case, 3 denotes a connector terminal, 11 denotes a valve which opens and closes an exhaust gas passage by vertical arrangement, 12 denotes a seat which maintains a degree of aperture in response to a vertical arrangement of the valve 11, 13 denotes a guide bush, 14 denotes a shaft with a valve 11 fitted to a lower end, 15 denotes a guide seal, 16 denotes a guide plate, 17 denotes a guide seal cover, 18 denotes a spring seat, 19 denotes a spring which pushes the shaft 14 in a direction of closure of the valve 11, and 20 denotes a motor. 21 denotes a rotor with a hollow space. A threaded portion is formed on an inner face of the hollow space.
22 denotes a coil, 23 denotes a yoke, 24 denotes a magnet, 25 denotes a slide ball, and 26 denotes a rotor shaft. A bearing, which supports an upper end of the rotor 21, comprises the slide ball 25 and the rotor shaft 26
27 denotes a bearing which supports a lower end of the rotor 21. 28 denotes a commutator which is integrally fitted to an upper end of the rotor 21. The motor brush 30 and the commutator 28 are arranged at a position on an upper end of the rotor 21 and below the bearing which supports an upper end of the rotor 21 which is composed of the rotor shaft 26 and the slide ball 25.
29 denotes a brush spring, 30 denotes a motor brush, 31 denotes a motor shaft which forms a threaded portion on an outer peripheral face. The threaded portion is threadably fitted to a threaded portion formed on an inner face of the hollow space of the rotor 21. 40 denotes a position sensor.
The operation of the conventional EGR valve device will be described below.
In this type of EGR valve, a fixed return torque is generated in a direction of closure of the valve 11 due to the spring 19, and a variable motor torque is generated in a direction of opening the valve 11 due to a current in one direction of the motor 20. Thus the opening and closing of the valve 11 is controlled by the balance of these torque components.
In the conventional EGR valve device comprised as discussed above, because a DC motor is used as a source of required torque to open and close the valves 11, a motor brush and a commutator are provided. The motor brush and the commutator are arranged below the slide ball 25 and on the upper end of the rotor 21. The rotor 21 itself can deviate vertically in an axial direction due to the repulsive force operating in an axial direction of the rotor 21 in conjunction with the opening and closing of the valve 11. Thus the problem has arisen that it is not possible to avoid adverse influence on a current carrying device such as a commutator or motor brush when a positional deviation of the rotor 21 occurs in an axial direction.
Furthermore, since the motor brush 30 and commutator 28 are arranged below the slide ball 25 and on the upper end of the rotor 21, the problem has arisen that motor failure is facilitated by foreign objects such as particulate matter generated by wear in the motor brush 30 entering the interior of the DC motor and accumulating in the gap between the magnet 24 and the rotating components of the motor such as the coil 22 or the like.
The current carrying device having the motor brush 30 and the commutator 28 is integrally fitted to an upper end of the rotor 21, and an upper end of the motor shaft 26 abuts with and rotates freely on the slide ball 25. Furthermore the rotating component of the motor such as the coil 22 is assembled so as to have a fixed gap with respect to the magnet 24. Thus the problem of low productivity during assembly has arisen.
The present invention is provided to solve the above-described problem, and the object of the present invention is to provide an EGR valve device which avoids adverse effects on the current carrying device by eliminating the possibility that the rotor will undergo a vertical deviation in an axial direction and which improves reliability of the device by preventing motor failure due to foreign objects such as particulate matter due to wear in the motor brush 30.
The present invention has the further object of providing an EGR valve which improves productivity when assembling the device.
The EGR valve device as defined by the present invention is provided with a motor rotating unit having a stator, in which each of a fixed number of coils is arranged in a peripheral direction of a stator core, and a rotor in which each of a plurality of magnets is fitted to an outer peripheral face corresponding to one coil of the stator, a valve drive mechanism for driving a valve linearly according to the rotation of the rotor of the motor rotating unit, a bearing for rotatably supporting the rotor, to which the magnets are fitted, with respect to the stator, and a current carrying device, which is arranged at a position placed on an outer side opposite to a side arranging the magnets on a rotational axis of the rotor with respect to the bearing, for commutating a direct current supplied from a power source according to a position of the rotor and supplying the commutated current to one coil of the stator.
With such a structure, it is possible to prevent adverse effects on the current carrying device due to the positional deviation of the rotor in an axial direction due to a repulsive force acting on the rotor when the valve driving mechanism drives the valve. Such adverse effects are prevented by the provision of the bearing arranged between the current carrying device and rotor which has the magnets. Thus it is possible to improve reliability of the valve device.
The EGR valve device as defined by the present invention is provided with the current carrying device comprising a plurality of slip rings, a plurality of commutator pieces and a plurality of motor brushes. A disk-shaped feeding unit comprises the slip rings and the commutator pieces, and the disk-shaped feeding unit is integrally fitted to an extension of the rotor which extends to the outer side opposite to the side arranging the magnets on the rotational axis of the rotor with respect to the bearing.
With such a structure, it is possible to prevent adverse effects on the slip rings and commutator pieces formed on the disk-shaped feeding unit due to the positional deviation of the rotor in an axial direction due to a repulsive force acting on the rotor when the valve driving mechanism drives the valve. Such adverse effects are prevented by the provision of the bearing arranged between the feeding unit and the rotor which has the magnets. Thus it is possible to improve reliability of the valve device.
The EGR valve device as defined by the present invention is provided with a shielding member which shields an opening between the motor rotating unit and the current carrying device.
In this way, it is possible to prevent motor failure that results from the accumulation of foreign objects in the rotating parts of the motor. The foreign objects (such as particulate matter) are generated as the parts of the current carrying device become worn. Thus it is possible to improve reliability of the valve device.
The EGR valve device as defined by the present invention is provided with the shielding member which is tightly fitted to an outer peripheral face of an outer ring of a bearing in which an inner peripheral face of an inner ring is tightly fitted to an outer peripheral face of the extension of the rotor to which the magnets are fitted. The shielding member seals the bearing, covers an open face of the motor rotating unit of the current carrying device and is arranged between the bearing and the current carrying device.
In this way, it is possible to prevent motor failure that results from the accumulation of foreign objects in the rotating parts of the motor. The foreign objects (such as particulate matter) are generated as the parts of the current carrying device become worn. Thus it is possible to improve reliability of the valve device.
The EGR valve device as defined by the present invention is adapted to assemble a current carrying device onto the extension of the rotor after assembling the rotating unit of the motor.
In this way, it is possible to perform assembly of the current carrying device in a separate process to the rotating unit of the motor and thus it is possible to improve productivity during assembly.